Abstract

We present an investigation into the environments of quasars with respect to galaxy clus-ters, and environment evolution with redshift and luminosity. The positions of quasarswith respect to clusters have been studied using cluster and quasar catalogues available,covering the redshift range 0.2 < z < 1.2. The 2D projected separations and the 3Dseparations have been found and the orientation of the quasar with respect to the majoraxis of the closest cluster calculated, introducing new information to previous work.The positions of quasars with respect to clusters of galaxies will give an indicationof the large scale environment of quasars and potentially clues as to which formationmechanisms are likely to dominate at various redshifts. For example, galaxy mergersare most likely to occur in galaxy group environments and will create luminous quasars.Galaxy harassment is more likely to occur on the outskirts of galaxy clusters and createlower luminosity AGN. Secular processes such as bar instability can also create AGN andare likely to be the cause of nuclear activity in isolated galaxies. The aim of this work isto study the large scale environment over a large redshift range and study the evolutionas well as any change in environment with quasar luminosity and redshift. Another aimof this work is to study the orientation of a quasar with respect to a galaxy cluster. Ifgalaxy clusters lie orientated along filaments, the position of a quasar with respect to acluster will give an indication as to where quasars lie with respect to the filament andtherefore the large scale structure.There is a deficit of quasars lying close to cluster centres for 0.4 < z < 0.8, indicatinga preference for less dense environments, in agreement with previous work. Studyingthe separations as a function of cluster richness, there was a change in quasars lyingcloser to poorer clusters for z < 0.2 (Lietzen et al. 2009) to lying closer to richer clustersfor 0.2 < z < 0.4, though more clusters at low redshifts will be needed to confirmthis. There is no obvious relation between the orientation angle between a quasar andthe major axis of the closest galaxy cluster and 2D projected separations. Using faint(Mr > −23.0 mag) and bright (Mr < −23.0 mag) quasars, there is no difference betweenthe two magnitude samples for the 2D separations or the cluster richness, in contrastto Strand et al. (2008) who found brighter quasars lying in denser environments thandimmer quasars. These is no change with redshift (over 0 < z < 1.2) in the positions ofthe quasars with respect to the cluster or the cluster richness as a function of absolutequasar magnitude. There is also no preferred orientation between the quasar and thecluster major axis for bright or faint quasars.Spectra of a selection of 680 star forming galaxies, red galaxies, and AGN were taken byLuis Campusano and Ilona S¨ochting and 515 redshifts calculated. Though few of thesegalaxies turned out to be cluster members as was originally intended, it was possibleto use these galaxies to study the environments of quasars with respect to star-forminggalaxies and galaxy clusters. The objects were classified (33 classed as AGN), and starformation rates calculated and compared. Three AGN and 10 star forming galaxies lieat the same redshift (z = 0.29) as three galaxy clusters. The three galaxy clusters havethe same orientation angle and may be part of a filament along with the star forminggalaxies and AGN. Further study will investigate the relation between AGN positionsand filaments of structure.A sample of quasar spectra taken by Lutz Haberzettl using Hectospec on the MMT weretaken to increase the number of quasars used in this study. However, when studyingthe spectra, a number of high redshift quasars showed evidence of ultra-strong UV Feiiemission in their spectra. The redshifts of these quasars were too high to be includedin the main body of the study. However, a significantly large number of ultra-strongUV Feii emitting quasars have been found in the direction of three LQGs in the redshiftrange 1.1 < z < 1.6, including the Clowes-Campusano Large Quasar Group (CCLQG).Ly� fluorescence can increase the UV Feii emission. However, Ly� emission from otherquasars was found to be negligible compared to emission from the quasar’s central source.Though there has been no previous indication that the LQG environment is unique, thehigh level of iron emission may indicate a difference in environment. Plans for futurework based on these results are outlined.